Open top housing type universal rolling mill

ABSTRACT

An improved open top housing type universal rolling mill construction is provided in which the roll gap adjustment of each roll is accomplished by moving the wedges of a pair of double wedge type roll gap adjusting mechanisms for each roll chock of the roll, and each top cross-beam for the open top housing is pivotally secured to the housing. Thus, this universal rolling mill construction is advantageous in roll changing, well suited for use as a tandem mill, and superior in rigidity.

United States Patent Aramaki 1 1 Sept. 30, 1975 OPEN TOP HOUSING TYPE UNIVERSAL 939.167 11/1909 Sack 72/244 x ROLLING MILL 3,212.314 10/1965 Sieger 72/244 X [75] inventor: Keiichi Aramaki, Fukuyama, Japan Primary E.\'aminer-Milton S. Mehr [73] Asslgnec' #235 53:11" Kabushlkl Kalsha' Attorney, Agent, or FirmFlynn & Frishauf [22] Filed: Aug. 14, 1974 [2]] Appl. No.: 497,189 [57] ABSTRACT An improved open top housing type universal rolling [30] Foreign Apphcanon Pnorm Data mill construction is provided in which the roll gap ad- Sept. 4. 1973 Japan 48-98919 justment f h r ll is accgmplished by moving the wedges of a pair of double wedge type roll gap adjust- [52] US. Cl; 72/238; 72/244 m mechanisms for each roll chock of the rolL and [5 l l Cl. 3 each top ross beam for the Open top housing is pivot- 1581 held of Search 72/228 ally secured to the housing. Thus, this universal rolling 72/244 mill construction is advantageous in roll changing. [56] R f C d well suited for use as a tandem mill, and superior in e erences lte rigidity UNITED STATES PATENTS 395.350 1/1889 Reese 72/228 5 Claims, 9 Drawing Figures Fig. I

IT I? US. Patent Sept. 30,1975 Sheet 2 of4 3,908,426

US. Patent Sept. 30,1975 Sheet 3 of4 3,908,426

US. Patent Sept. 30,1975 Sheet 4 of4 3,908,426

Fig.6 7 Fig.7

47 i] H 3 46 25 5 D OPEN TOP HOUSING TYPE UNIVERSAL ROLLING MILL BACKGROUND OF THE INVENTION The present invention relates to an open top housing type universal rolling mill of the stand changing type which is used mainly for continuous rolling or finish rolling of H-section steels.

As well known in the art, the following conditions are required for a continuous rolling mill:

1. Lightness, simplicity of construction and low cost:

In the case of continuous rolling, 6 to 8 universal rolling mills are usually required. Therefore, if the cost of each mill is high, the entire equipment cost will become 3 to 4 times the equipment cost for a reverse rolling which requires only a single roughing mill and a single finishing mill. Consequently, each of the universal rolling mills must be light in weight, simple in construction and as low as possible in cost.

2. High rigidity of mill:

Particularly in the case of continuous rolling, variation in the rolling conditions due to a disturbance caused by temperature variation, etc. of a materialin a rolling mill results in a change of the tension between this rolling mill and the next rolling mill, and this change of the tension successively changes the rolling conditions to eventually give rise to a defect of shape in the final product. Therefore, it is necessary that each rolling mill has a specially high rigidity.

3. Reduction in roll changing time:

In the case of the continuous rolling which requires a large number of rolling mills, though the roll changing time on each stand may not be so great, the roll changing for the entire mills requires much time and hence a large number of operators, thus requiring a highly efficient roll changing operation.

4. Reduction in the range of on-line adjustments of roll reduction by rolls:

While, in the case of a reverse rolling, each blank is subjected to 7 to 11 reverse rolling passes by a roughing mill accomplishing about 15 to 20% reduction through each pass and therefore each stand must be constructed to permit a wide range of roll gap adjustments, in the case of the continuous rolling a blank entering each stand is subjected only to a single rolling pass and therefore the range of adjustments required for each stand is needed only to compensate for variations in the various conditions relative to the set points, thus leaving room for simplification in the rolling mill construction.

Rolling mills of various types are known in the art, and each of these types of mills has its own problems as will be described hereunder. For example, with the universal rolling mills of the roll changing type in which each stand itself is fixedly secured on the mill line and only the rolls are changed, the C hook roll changing method in which each horizontal roll is removed by for example an overhead crane using a C hook is disadvantageous in that while the left and right vertical rolls are first opened widely to be clear of the top roll and they are then pulled up after which the top and bottom rolls are pulled up by meand of the C hook, the use of the crane results in a longer roll changing time and moreover the rolling operation must be interrupted during the roll changing cycle, thus deteriorating the operating efficiency. Another disadvantage is that since the vertical rolls must be pulled out to the positions where they are entirely clear of the top roll so as to be pulled up, the yoke for each vertical roll must be overhung considerably with the result that the stand housing must be increased in size to improve the rigidity of the mill. There is another method of the roll changing type that is known as the cross-beam method in which the corssbeams connecting the two housings together are utilized in changing the rolls to remove or insert the roll equipped with its chocks through the housing window. While this method is convenient and is capable of varying the roll barrel length in accordance with the size of a piece to be rolled with the resultant advantage of reducing the deflection of the rolls and hence the weight of the rolls, there is a disadvantage that the bulky housing is required due to its large window. Another disadvantage is that in transmitting the rolling force of the top and bottom rolls to the rolls, chocks, cross-beams, screws and housings, the provision of the cross-beams between the screws and the roll chocks tends to increase the clearances on the whole. Still another disadvantage is that as in the case of the C hook method, the rolling operation must be interrupeted during the roll changing cycle and moreover the zero adjustment between the rolls as well as other adjustments attendant to the rolling must be effected after the rolls have been changed, thus requiring a roll changing time which is about two times the roll changing time required for the rolling mills of the stand changing type that will be described hereunder. With the mill of the stand changing type in which the stand assembly is removed from the mill line and a new one having all the necessary equipment is installed on the mill line in place of the removed stand, there is the disadvantage of requiring the use of a large capacity crane, although there is an advantage that as compared with other known arrangements, the time during which the rolling operation must be interrupted isthe shortest due to the fact that the stand having all the necessary equipment including the rolls is picked up. With another arrangement of the stand changing type in which the stand is pulled out by a push pull device or the like over a track crossing the mill line at right angles and a preliminarily equipped new one on a transverse carriage is inserted into place by the push pull device, the construction and arrangement of the push pull device and the track present a difficult problem, although the roll changing time required is the shortest as compared with those of the abovementioned conventional arrangements. With still another method which is called as the inner stand method and in which the reaction force of the vertical rolls is borne by the inner housing, the rolling force of the horizontal rolls is borne by the outer stand and only the inner housing is changed together with the rolls, with the stand itself being fixedly secured on the mill line. A disadvantage of this method is that since the housing consists of the inner and outer portions, as compared with rolling mills of the one piece type, more clearance is present and moreover the roll changing time is the same with those of the previously described arrangements of the roll changing type. While, in addition to these, there are other types of mills such as a three-piece prestress type mill, etc., they have their own problems that must be solved.

SUMMARY OF THE INVENTION With a view to overcoming the foregoing difficulty, it is the object of the present invention to provide an open top housing type universal rolling mill comprising a housing of the open top construction, top crossbeams rotatable between open and closed positions by means of pins or the like. vertical roll yokes of the over hang type, and a plurality of roll gap adjusting mechanisms of the wedge type, thereby ensuring a high rigidity, simple and lightweight mill construction and reduced roll changing time.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side view looking in the direction of the arrow line II of FIG. 2, showing an embodiment of an open top housing type universal rolling mill according to the present invention;

FIG. 2 is a front view of the embodiment of FIG. 1 with part thereof broken away;

FIG. 3 is a plan view showing the vertical roll portion in the embodiment of FIG. 1;

FIG. 4 is a view looking in the direction of the arrow line IVIV of FIG. 3;

FIG. 5 is a view looking in the direction of the arrow line V-V of FIG. 3;

FIG. 6 is a plan view showing the non-drive side chock of the horizontal roll in the embodiment of FIG.

FIG. 7 is a side view of FIG. 6;

FIG. 8 is a view showing the manner in which the roll is deformed and the chock is rotated by the rolling reaction force; and

FIG. 9 is a section view showing the non-drive side of the horizontal roll in the embodiment of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention will now be described in greater detail with reference to FIGS. 1 through 9 of the accompanying drawings in which atop roll 1 is provided on its necks with chocks 6 and 6 with their respective bearings, and a bottom roll 2 is similarly provided with chocks 7 and 7'. Each of the chocks 6 and 6' is provided on its upper sides with a pair of pressure blocks 31 and 31, and each of the chocks 7 and 7 is provided on its lower sides with a pair of pressure blocks 31" and 31". The thickness of the pressure blocks 31, 31, 31" and 31" is selected to suit the barrel diameter of the rolls, and that face of each pressure block which contacts with the chock is cylindrical and the other face thereof is flat. Also wedges 11, 11', 12, 12, 13, l3, l4 and 14' are respectively arranged to be in contact with the smooth faces of the corresponding pressure blocks to receive the rolling reaction force. Each of the pressure blocks may for example be an antifrictional piece composed of a forging lined with a bearing material, and the pressure blocks of several different kinds of thickness are prepared to suit the barrel diameter of various rolls to be changed.

Each of the wedges 11, 11', 12 and 12 associated with the top roll 1 is formed with a female screw bore therethrough, and the turning of threaded rods 15, 15', 16 and 16' fitted in the female screw bores causes each wedge to move in a plane parallel to the rolled surface of a piece to be rolled and in a direction normal to the direction of travel of the piece. The turning of the screw rods l5, 15, 16 and 16 is accomplished by means of motors l8 and 19 through reduction gears 24 and 25, and in this way the position of the top roll 1 is adjusted. On the other hand, each of the wedges 13,

l3, l4 and 14 associated with the bottom roll 2 is similarly formed with an internally threaded hole therethrough so that when screw rods 17 and 17 which are fitted into the threaded holes are turned, each of the wedges 13, 13, 14 and 14 is moved in a plane parallel to the rolled surface of the piece to be rolled and in a direction normal to the direction of travel of the piece.

Contrary to the top roll position adjusting screw rods 15,15, 16 and 16', the screw rods 17 and 17' do not obstruct the changing of the top and bottom rolls and therefore each of the screw rods 17 and 17' consists of a single reverse screw rod which has oppositely threaded portions and which is common to the wedges 13 and 13' or the wedges l4 and 14'. Consequently, when the screw rods 17 and 17 are turned by means of a motor 20 through a reduction gear 26, the paired wedged l3 and 13 and the paired wedges l4 and 14' which are respectively threadedly mounted on the associated screw rods in opposite relation with each other are rotated in the opposite directions with each other.

The rolling reaction force imposed on the wedges ll, 1 l, 12 and 12 is borne by top cross-beams l0 and 10' provided on these wedges so that the reaction force is transmitted to the housing through pins 32 and 32' which are provided at the ends of the cross-beams. The top cross-beams l0 and 10' are pivotally mounted respectively by the pins 32 and 32' of a predetermined dimensional accuracy which permits no looseness, and the cross-beams 10 and 10 are respectively movable about the pins 32 and 32' to open and close in accordance with the operation of fluid pressure actuators 29 and 29' which are respectively attached to the associated cross-beam and the housing. The cross-beams 1G and 10' are also fixedly held in position respectively by the operation of fluid pressure actuators 37 and 37' which are mounted on the housing. In other words, in the present embodiment the top cross-beams 10 and 10 are provided with holes at the ends thereof which are opposite to the pins 32 and 32', and pins 49 and 49 of a predetermined dimensional accuracy as mentioned earlier are moved into or out of the holes in the top cross-beams in their horizontal position in accordance with the fluid pressure applied by the rods of the fluid pressure actuators 37 and 37 to thereby firmly hold the cross-beams against the housing or release them from the locked position.

It should be apparent that the abovedescribed opening and closing mechanisms and the locking mechanisms for the top cross-beams may of course be composed of other means such as a gear mechanism, and the basic idea of this invention is in no way limited by differences in the construction of these mechanisms.

Top roll balancing fluid pressure actuators 30 and 30 are respectively mounted on the top cross-beams 10 and 10' at the central portions thereof, and the ends of rods 30" and 30" of the actuators are T-shaped so that when the rods 30" and 30" are respectively in a predetermined position, their T-shaped ends can freely move in and .out of the associated engaging slots formed in the upper portions of the top roll chocks 6 and 6, whereas when the rods 30" and 30" are turned degrees from their predtermined position, the T- shaped ends engage with the associated roll chocks. In other words, when the rods 30" and 30" are in the predetermined positions relative to the chocks 6 and 6, the fluid pressure actuators 30 and 30' are out of engagement with the chocks 6 and 6' to permit the crossbeams and 10 to rotate between the open and closed position, whereas when the rods 30 and 30" are in the positions 90 displaced from the predetermined position the chocks 6 and 6 are pulled up in response to the operation of the fluid pressure actuators 30 and 30'.

In each of the non-drive side chocks 6 and 7 of the top and bottom roll chocks, as shown in FIG. 9, the roll neck bears the force in the radial direction of the roll through cylindrical roller bearings 38 and the axial thrust force is borne through the intermediary of thrust bearings 39 used in combination with taper roller bearings. The outer ring of the thrust bearings is fastened to a sleeve 40 by a nut 41, and a toothed gear 42 which is fitted threadedly on the outer surface of the sleeve 40 is rotated by a pinion 43 which is in mesh with the former. The sleeve 40 is key jointed to the external portion to prevent the rotation of the sleeve 40 so that as the toothed wheel 42 is rotated by the rotation of the pinion 43, the sleeve 40 threadedly engaged with the toothed wheel 42 is caused only to slide in the axial direction. With the arrangement just described, the axial adjustment of the position of the chocks 6 and 7' relative to the top and bottom rolls 1 and 2 may be accomplished as desired. Further, the inner ring of the thrust bearings is fastened to the roll through :an intermediary piece.

On the other hand, though not shown in the drawings, each of the drive side chocks 6 and 7 is provided with an axial free clearance to absorb the axial roll adjustments, the thermal expansion of the roll and other allowances. The thrust force loaded on the chocks 6, 6, 7 and 7' is transmitted from a pin 45 provided on each side thereof to the housing through slide blocks 46, the pressure blocks 31, 31, 31" and 31" and the wedges 11, 11, 12, 12, 13, 13', 14 and 14'. In other words, the slide block 46 is movably fitted on the pin 45 at each side of each of the chocks 6, 6, 7 and 7', and slots 47 into which the slide blocks 46 may be slidably fitted are formed in the inner wall portion of the housing so that in response to the thrust due to the bending or the like of the rolls 1 and 2, the chocks 6, 6, 7 and 7 are rotated about the pivot pins 45 and their horizontal axial movement is prevented. The vertical movement of the chocks 6, 6, 7 and 7' is prevented by means ofthe wedges 11, ll, 12, 12', l3, 13', 14 and 14 and the housing through the pressure blocks 31, 31', 31" and 31" each having a cylindrically surfaced seat.

Vertical rolls 3 and 4 are respectively supported by chocks 8 and 9 which are respectively mounted between yokes 5a and 5a and between yokes 5b and 512. These yokes are supported by the housing in an over hang manner. As shown in FIGS. 3 through 5, the chocks 8 and 9 are respectively mounted horizontally slidably between the yokes 5a and Sa'and between the yokes 5b and 5b, and the rolling reaction force is borne by the yokes constituting part of the housing through pressure blocks 33 and 34 having a suitable thickness corresponding to the dimensions, etc. of a H-section to be rolled and the vertical roll diameter, and through wedges 22, 22', 23 and 23 which are respectively arranged vertically relative to the yokes 5a, 5a and 5b, 5b. The pressure blocks 33 and 34 are similar to the pressure blocks 31, 31, 31" and 31 for the housing which is associated with the previously described top and bottom rolls. Each of the wedges 22, 22', 23 and 23 is provided with a cutout 35 at its lower portion as shown inFIG. 5, and in accordance with the turning of screw rods by motors 21 and 21 through reduction gears 27, 28, 27' and 28 each of the wedges is moved in a plane parallel to the rolled surface of the piece to be rolled and in a direction normal to the direction of travel of the piece.

The roll changing operation on the top and bottom rolls 1 and 2 is effected in the following manner starting at the top of the mill. Firstly, the fluid pressure of the top roll balancing actuators 30 and 30 is released and then the actuator rods are rotated until they are brought out of engagement with the slots provided in the top roll chocks 6 and 6, after which the fluid pressure actuators 37 and 37' are operated to move the pins 49 out of the top cross-beams 10 and 10 and then the fluid pressure actuators 29 and 29' are operated to rotate the top cross-beams 10 and 10 through into the open position. Thereafter, the screw rods l5, l5, l6 and 16' are rotated by the motors l8 and 19 through the reduction gears 24 and 25 to recede outwardly the top wedges 11, 11', 12 and 12' into the open position shown by the phantom line in FIG. 2. When these operations have been completed, the top roll 1 is in condition for the lifting operation. The bottom roll 2 is lifted in a similar manner, but after the vertical rolls 3 and 4 have been receded to either sides as will be described later. The position of the bottom roll 2 is adjusted through the pressure blocks 31" and 31" by turning the screw rods 17 and 17' through the reduction gear 26 from the motor 20 to cause the wedges 13, 13, 14 and 14' to slide to either sides.

The roll change of the vertical rolls3 and 4 is accomplished by moving the wedges 22, 22', 23 and 23' respectively to a position as shown by the phantom line in FIGS. 4 and 5 by means of the motors 21 and 21' through the reduction gears 27, 28, 27 and 28' thereby to permit an ,end 36 of each of the chocks 8 and 9 to move in and out of the cutout portion 35 provided in the lower portion of each wedge. In FIG. 3, numeral 48 designates a vertical roll balancing fluid pressure actuator which is mounted on each of the yokes 5a, 5a, 5b and 5b for positioning the vertical rolls 3 and 4 mounted respectively in the chocks 8 and 9 through the wedges 22, 22', 23 and 23'. By removing the wedges, the chocks 8 and 9 may be respectively pulled out to the left and right. The roll gap adjusting mechanism for each vertical roll is similar to that previously described in connection with the top and bottom rolls, and therefore it will not be described in any detail.

With the rolling mill of this invention which is constructed as described above, by virtue of the fact that each of the wedges is moved in a plane parallel to the rolled surface of a piece to be rolled and in a direction normal to the direction of travel of the piece, that all the roll gap adjusting mechanisms for the top and bottom rolls and the vertical rolls are fixedly secured to the stationary housing, and that the top cross-beams 10 and 10' are designed to receive the rolling reaction force of the top roll only through the pressure receiving surfaces of the wedges, .the assembly of the cross-beams 10 and 10' constituting the movable part of the mill is simplified and thus the top cross-beams 10 and 10 are prevented from interfering with the roll gap adjusting mechanisms during roll change of the top and bottom rolls 1 and 2. Further, since the axial adjusting mechanism is provided on the non-drive side of each of the top and bottom rolls 1 and 2 so that the rolls may be directly adjusted in the axial direction without moving the chocks 6, 6, 7 and 7 and since each chock is rotatably supported by the pins 45 and the slide blocks 46 which are provided on the sides thereof when the load is applied to the top and bottom rolls and they are deformed by the rolling reaction force during the rolling operation as shown exaggeratedly in FIG. 8 and since each of the blocks 46 is fitted in the guide slot 47 in the housing, even when the roll is deformed or the chock is inclined the center of the chock at the central axis of the pins remains unchanged with less detrimental effect on the roll gap adjusting mechanisms. Furthermore, during the rolling of a H-section steel by the top and bottom rolls, owing to the fact that the parts of each roll including the radial bearing sections are symmetrical on both sides of its barrel portion, both of the roll chocks have the same angle of inclination and consequently there will be no unbalance in the vertical movement of the chocks on the sides of the roll owing to the said structure thereof. Further, since each of the pressure blocks 31, 31', 31" and 31" has a cylindrical surface or spherical surface, they are maintained in close contact with the inclined surfaces of the wedges when the chocks 6, 6, 7 and 7' are inclined.

Moreover, with the rolling mill of this invention, since each of the top and bottom rolls and the vertical rolls is provided with a pair of wedges at each end thereof to receive the rolling reaction force, by moving the wedges to the position shown by the phantom line in FIGS. 2 and 5, it is possible to easily pull up or pull down the top and bottom rolls from the above to remove or insert them and to pull out the vertical rolls respectively to the left and right during the roll change. By virtue of the fact that the top and bottom rolls are pulled up to accomplish the roll change, with the rolling mill according to the invention, the width of the housing window is smaller than the roll diameter and hence the rigidity of the mill itself is improved and its construction is simplified. Still furthermore, a rolling roll can generally stand regrinding for several times and therefore the difference in roll diameter between the roll to be replaced and the new one is on the order of Consequently, the screwdown adjustments have been accomplished by means of screws. According to the present invention, however, before installation in the mill, the pressure blocks 31, 31', 31" and 31 which are to be mounted on the chocks are prepared in several different kinds of thickness and the pressure blocks of a suitable thickness corresponding to the barrel diameter of the rolls are selected for installation, thereby reducing the range of adjustments by the wedges themselves and providing a great advantage from the design point of view.

It will thus be seen from the foregoing description that the universal rolling mill according to the present invention is very simple in construction and light in weight on the whole, yet is possesses a high degree of rigidity with the result that a set of accessories such as the sole plate, the rail lifting device, the stand push pull device and the transverse carriage may be reduced in size and weight, thus making it possible to arrange an ideal mill line for continuous rolling as well as finish rolling. The industrial utility of the present invention is therefore very great.

What is claimed is:

1. An open top housing type universal rolling mill comprising:

an open top housing;

top, bottom and vertical rolls mounted in said housa chock associated with and coupled to each of said top, bottom and vertical rolls;

said housing having a housing window in the vicinity of each of said docks;

a pair of double-wedge roll gap adjusting means coupled to each of said chocks, said pair of roll gap adjusting means of said each chock each comprising wedges arranged adjacent to the inner surface of a respective housing window for guiding said roll associated with said each chock, each of said wedges of said pair of roll gap adjusting means being movable and adjustable in a plane substantially parallel to the corresponding plane of a plurality of rolling planes of said rolling mill and in a direction normal to the direction of travel of a piece to be rolled.

2. A universal rolling mill according to claim 1 further comprising means for rotatably supporting each of said chocks mounted on each of said top and bottom rolls in response to a rolling force on said roll and the deflection of said roll due to said rolling force, and means coupled to said chocks for maintaining the central axis of rotation of said chock unchanged against horizontal and vertical forces.

3. A universal rolling mill according to claim 2, wherein said means for rotatably supporting the chock and said means for maintaining said central axis of rotation unchanged against the horizontal force acting thereon comprises a slide block rotatably mounted by a pin on each side of said chock and fitted in a slot provided in the inner wall of said housing to permit said chock to slide vertically, and wherein said means for maintaining said central axis of rotation unchanged against the vertical force comprises a plurality of pressure blocks each having a circular seat for contacting with a circular seat on the upper or lower surface of said chock to' bear the vertical force.

4. A universal rolling mill according to claim 1 further comprising a top cross-beam assembly detachably mounted on said open top housing by means of a plurality of pins.

5. A universal rolling mill according to claim 4, wherein said top cross-beam assembly includes a pair of top cross-beams; two pins securing each of said top cross-beams to said housing; first fluid pressure actuator means coupled to each of said top cross-beams for raising said top cross-beams through degrees about one of said pins; and second fluid pressure actuating means coupled to the other of said pins of said top cross-beams for detaching same from said top crossbeams. 

1. An open top housing type universal rolling mill comprising: an open top housing; top, bottom and vertical rolls mounted in said housing; a chock associated with and coupled to each of said top, bottom and vertical rolls; said housing having a housing window in the vicinity of each of said docks; a pair of double-wedge roll gap adjusting means coupled to each of said chocks, said pair of roll gap adjusting means of said each chock each comprising wedges arranged adjacent to the inner surface of a respective housing window for guiding said roll associated with said each chock, each of said wedges of said pair of roll gap adjusting means being movable and adjustable in a plane substantially parallel to the corresponding plane of a plurality of rolling planes of said rolling mill and in a direction normal to the direction of travel of a piece to be rolled.
 2. A universal rolling mill according to claim 1 further comprising means for rotatably supporting each of said chocks mounted on each of said top and bottom rolls in response to a rolling force on said roll and the deflection of said roll due to said rolling force, and means coupled to said chocks for maintaining the central axis of rotation of said chock unchanged against horizontal and vertical forces.
 3. A universal rolling mill according to claim 2, wherein said means for rotatably supporting the chock and said means for maintaining said central axis of rotation unchanged against the horizontal force acting thereon comprises a slide block rotatably mounted by a pin on each side of said chock and fitted in a slot provided in the inner wall of said housing to permit said chock to slide vertically, and wherein said means for maintaining said central axis of rotation unchanged against the vertical force comprises a plurality of pressure blocks each having a circular seat for contacting with a circular seat on the upper or lower surface of said chock to bEar the vertical force.
 4. A universal rolling mill according to claim 1 further comprising a top cross-beam assembly detachably mounted on said open top housing by means of a plurality of pins.
 5. A universal rolling mill according to claim 4, wherein said top cross-beam assembly includes a pair of top cross-beams; two pins securing each of said top cross-beams to said housing; first fluid pressure actuator means coupled to each of said top cross-beams for raising said top cross-beams through 90 degrees about one of said pins; and second fluid pressure actuating means coupled to the other of said pins of said top cross-beams for detaching same from said top cross-beams. 